Both Seattle Genetics and Pieris have been busy on the deal front lately, and today their lists grew longer as the two pair for a potential $1 billion-plus biobucks pact in immuno-oncology.

As ever, the upfront cost is much smaller, just $30 million; but if everything goes perfectly well, and there are approvals and big sales, this could swell into $1.2 billion in biobucks terms.

The deal sees the biotechs work together on developing a series of targeted bispecific immuno-oncology treatments for solid tumors and blood cancers.

Pieris brings to the table its “agonistic costimulatory Anticalin proteins,” that it says when fused to a tumor-targeting antibody can “activate the immune system preferentially in the tumor microenvironment.”

The Anticalin proteins are engineered versions of endogenous low-molecular weight human proteins called lipocalins. Pieris thinks the nature of its proteins give them high affinity and specificity, and make them suitable for use in bispecific therapeutics.

Seattle Genetics, meanwhile, will bring its work in antibody-drug conjugates (ADCs), which targets and tumor-specific mAbs, from which programs will be selected for the collab. The bispecific drug candidates coming out of this pact will be designed to enable the patient’s immune cells to specifically attack tumors, the pair said in a statement.

The companies will hunt out multiple Antibody-Anticalin fusion proteins during the research phase of the deal, and Seattle can pick up to three programs for further development.

And, before any pivotal trial, Pieris can also opt into global co-development and U.S. sales of the second program, while also sharing in global costs and profits on a 50-50 basis. Seattle Genetics will, however, develop, fund and sell the other two programs on its own.

“As the industry leader in ADCs, we bring deep expertise in targeted cancer therapy development to this collaboration with Pieris,” said Dennis Benjamin, Ph.D., SVP of research at Seattle Genetics.

“Pieris’ Anticalin technology and Antibody-Anticalin bispecific approach are intended to overcome the limitations of currently available immuno-oncology products. This partnership leverages our cancer targets and tumor-specific antibodies to explore multiple novel bispecific combinations, with the goal of developing targeted therapies that improve outcomes for people with cancer.”

A few weeks ago, Seattle spent $614 million on a buyout deal for Cascadian Therapeutics, getting its hands on tucatinib, an oral tyrosine kinase inhibitor, which is pivotal midstage tests for advanced HER2 breast cancers.

This comes after Seattle last summer called a halt to all clinical testing of vadastuximab talirine (SGN-CD33A) after seeing a higher rate of patient deaths with the drug in a phase 3 trial; this came before a multibillion-dollar deal to buy Immunomedics fell through last May.

“Pieris was the first company to bring a tumor-targeted costimulatory bispecific to patients with PRS-343, and we are looking forward to broadening our bispecific pipeline through this alliance. Seattle Genetics is a compelling partner for Pieris with a long-standing commitment to oncology,” added Stephen Yoder, president and CEO of Pieris.

Pieris, meanwhile, has also been ramping up the deals: Just over a year ago, it penned a €30 million ($31.5 million) deal with France’s Servier for rights to a PD-1-targeting bispecific checkpoint inhibitor and four other immuno-oncology candidates.

It also has deals with Roche and a major biobucks deal with AstraZeneca, although last May it was hit by some bad news when Daiichi ditched work on the biotech’s anti-PCSK9 Anticalin-Albumod DS-9001 in a phase 1 dyslipidemia test, given poor results.